Asymptotic levels of the $A$ $^{1}\ensuremath{\Sigma}_{u}^{+}$ state of the two isotopomers $^{39}\mathrm{K}_{2}$ and $^{39}\mathrm{K}^{41}\mathrm{K}$ up to the dissociation limit are investigated with a Doppler-free high resolution laser-spectroscopic experiment in a molecular beam. The observed level structure can be reproduced correctly only if a mass dependent correction term is introduced for the interaction potential. The applied relative correction in the depth of the potential is ${10}^{\ensuremath{-}6}$, which is in the order of magnitude expected for corrections of the Born-Oppenheimer approximation. A similar change in ground state potentials might lead to significant changes of mass-scaled properties describing cold collisions like the $s$ -wave scattering length.Asymptotic levels of the $A$ $^{1}\ensuremath{\Sigma}_{u}^{+}$ state of the two isotopomers $^{39}\mathrm{K}_{2}$ and $^{39}\mathrm{K}^{41}\mathrm{K}$ up to the dissociation limit are investigated with a Doppler-free high resolution laser-spectroscopic experiment in a molecular beam. The observed level structure can be reproduced correctly only if a mass dependent correction term is introduced for the interaction potential. The applied relative correction in the depth of the potential is ${10}^{\ensuremath{-}6}$, which is in the order of magnitude expected for corrections of the Born-Oppenheimer approximation. A similar change in ground state potentials might lead to significant changes of mass-scaled properties describing cold collisions like the $s$-wave scattering length.

arXiv:0706.2290Physical Review AJul 31, 20077 citations

Asymptotic levels of the

A

$^{1}\ensuremath{\Sigma}_{u}^{+}$ state of the two isotopomers

^{39}\mathrm{K}_{2}

and

^{39}\mathrm{K}^{41}\mathrm{K}

up to the dissociation limit are investigated with a Doppler-free high resolution laser-spectroscopic experiment in a molecular beam. The observed level structure can be reproduced correctly only if a mass dependent correction term is introduced for the interaction potential. The applied relative correction in the depth of the potential is ${10}^{\ensuremath{-}6}$, which is in the order of magnitude expected for corrections of the Born-Oppenheimer approximation. A similar change in ground state potentials might lead to significant changes of mass-scaled properties describing cold collisions like the

s

-wave scattering length.